This invention relates to a guarding system of a credit card against unauthorized use, particularly to one in which the data stored in a credit card will synchronously and automatically be replaced by the computer of a credit card issuing bank every time when a credit card is finished in trading. Thus, even if a credit card is faked, this faked credit card cannot be used because its data do not coincide with those renewed by the credit card issuing bank, surely preventing a credit card from copied and used fraudulently.
In accordance with the statistical data issued by the United Credit Card Center, in the year of 2001, Taiwan is next to none among Asian countries in xe2x80x9cthe fraud-loss basic pointxe2x80x9d of credit cards, and the loss of the amount of money due to faked credit cards makes a record last year. Especially, the rate of the fraud-loss basic point of credit cards is doubled up to four thousandths from May to August in the year 2001.
Credit card traders say that the xe2x80x9cfraud-loss basic pointxe2x80x9d of credit cards is usually maintained less than one thousandth in most credit card markets, but amazingly Taiwan is four times surpassing the other credit card markets in the world. Besides, bankers find that the time-limited efficacy of unauthorized use of credit cards by fraud is becoming faster and faster. In the past, the group of using illegally credit cards by fraud used to spend two or three days using up the amount of money of a credit card, but nowadays it takes only one day to do that. Therefore, the problem of how to prevent credit cards from faked and illegally used by fraud must be solved as soon as possible.
According to statistics, the probability of illegally using credit cards by fraud in most rations in the world is around seven ten thousandths, but it is up to three thousandths in Taiwan, which is four times more than an average value in the world, that is, among ten thousand credit card holders, thirty holders"" credit cards have been used by fraud. According to the statistics issued by the largest five international credit card issuing organizations, the sum paid by faked credit cards in Taiwan is up to NT$0.3 billion in the year 2000, which is {fraction (4.1/1000)} of the total amount of the credit cards used, with a rate of crime in faking credit cards and using them by fraud being next to none in Asian regions. In addition, the skill of committing crime in faking credit cards in a small amount is being developed into faking credit cards in a large amount by means of chips, and these faked credit cards are sold to indefinite persons for using by fraud, consequently increasing difficulty of prevention.
At present, a credit card is provided with a set of fixed word series as a code, which is confirmed by the bank computer for judging whether to carry on trading or not. In this case, so long as the code of a credit card is copied by fraud to duplicate a new credit card, illegally using credit cards by fraud is easy and unpreventable.
The objective of the invention is to offer a guarding system of a credit card against unauthorized use, in which one or more sets of letter-and-number series composed of letters and numbers are stored in the credit card, and the credit card issuing bank also has the same letter-and-number series as those of the credit card set up in its data archives. Thus, when a credit card is used in trading, the computer of the credit card issuing bank will check whether or not the data of the letter-and-number series of the credit card being used coincide with those in its data archives, and judge whether to let the trading carried on or not after confirmed. Besides, every time after the credit card is finished trading, the letter-and-number series of the credit card will synchronously and automatically be renewed by the computer of the credit card issuing bank, and then checked and stored in the data archives, achieving effect of preventing a credit card from illegally used by fraud.